In a known intake apparatus of an internal combustion engine, a construction in which an inertia supercharging effect is utilized is known. According to the inertia supercharging effect, an EGR gas is introduced to a surge tank and a lot of intake air is suctioned into a combustion chamber by means of pulsation and resonance of the intake air. According to the intake apparatus of the internal combustion engine, in order to exercise the inertia supercharging effect, a length of an intake port from the surge tank to the combustion chamber of the internal combustion engine is necessarily secured to some extent. Thus, in a case where the EGR gas is introduced to the surge tank, time is required for the EGR gas from being introduced to the surge tank to actually enter the combustion chamber of the internal combustion engine. As a result, a difference in time between timing at which the EGR gas is introduced to the surge tank and timing at which the EGR gas is actually introduced to the combustion chamber becomes large, which leads to inconvenience where transient responsiveness of the EGR gas decreases.
Therefore, a known intake apparatus of an internal combustion engine is proposed to distribute gas to plural intake pipes which are connected to plural cylinders of the internal combustion engine so as to introduce the gas to each intake port. Such intake apparatus of the internal combustion engine is disclosed, for example, in Japanese Patent Application Publication 2006-241992 and Japanese Patent Application Publication 2003-239816, for example.
Japanese Patent Application Publication 2006-241992 discloses an intake manifold including a collection pipe (surge tank), branch pipes (intake pipes) branched into four from the collection pipe, and a gas passage connected to each of the branch pipes to distribute a PCV gas thereto. According to the intake manifold disclosed in Japanese Patent Application Publication 2006-241992, the gas passage is connected to each of the branch pipes in the vicinity of an engine. As a result, the PCV gas is configured to be introduced to the branch pipes from a PCV gas inlet port provided in the vicinity of the engine.
In addition, Japanese Patent Application Publication 2003-239816 discloses an intake manifold including branch passages (intake pipes) which are connected to a collector (surge tank) and to a cylinder head and which are branched into four. The intake manifold disclosed in Japanese Patent Application Publication 2003-239816 includes a collector-side flange portion provided at a connection portion between the branch passages and the collector. A distribution path supplied with a PCV gas and branch paths introducing the PCV gas to the respective branch passages from the distribution path are provided at the collector-side flange portion. That is, the PCV gas is configured to be introduced to the branch passages from a PCV gas inlet port provided in the vicinity of the collector.
The construction of each of the PCV gas inlet ports disclosed in Japanese Patent Application Publication 2006-241992 and Japanese Patent Application Publication 2003-239816 is applicable to a construction of an EGR gas inlet port.